.btn {
    border-radius: 10px;
    padding: 5px 10px;
    border: 1px solid #ccc;
    display: flex;
    justify-content: center;
    font-size: 12px;
}
.footer {
    display: flex;
    justify-content: space-around;
}
.operation_box {
    padding: 10px;
    margin-bottom: 100px;
}